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  • Philips RC5 IR Decoder
    intervals followed by 1 longer interval followed by 6 short intervals followed by 3 long intervals followed by 4 shorts one long and 2 shorts There are 21 intervals total but this will vary depending on the code The first start bit is always 1 and is not decoded The output will be 1100001011100 where the MSB or second start bit is on the left The last entry in the data list is a 2 which denotes the end P Phase I Invert TI Time interval 890uS or 1 778mS 0 or 1 DATA 0 0 0 0 1 0 0 0 0 0 0 1 1 1 0 0 0 0 1 0 0 2 11100001011100 CLS READ TI IF TI 0 THEN P 0 I 0 IF TI 1 THEN P 1 I 1 this condition occurs when the second start bit is 0 WHILE TI Generating specific codes using a PC and a QBasic program In the schematic above a 555 timer and IR LED are used to produce a 36KHz IR transmission controlled by the PC printer port which can be copied into a learning remote control The printer port connection can be any one of the 8 data lines to the port The PC used was a HP Pavilion 6638 with a 533 MHz processor running Windows 98 Later versions of Windows do not allow direct control of the printer port and will not work Some version of MSDOS or Win95 could also be used The example program transmits the code 11011101001111 which represents the toggle bit off address 29 and data 15 which is not a standard RC5 code since address 29 is unassigned to any device The code was translated to a data list where 220 is the delay time needed to gate the 555 oscillator on for a period of about 1 8mS and 110 is the time for a approximate 890uS period These values may need adjustment for faster or slower PCs I measured the length of the entire 14 bit transmission with a scope and set the numbers for a 25mS total length The example waveform to produce the code of 11011101001111 is entered in a data list which represents either a short interval of about 890uS or a longer interval of about 1 8mS Each positive interval represents the time the 36KHz oscillator is running while the negative intervals represent the time the oscillator is off Each narrow positive interval transmits about 33 cycles of IR at a frequency of 36KHz The program waits for a keypress and then transmits the code twice with a separation of about 100mS The transmission can be copied into a learning remote control held a couple inches away from the IR LED The red LED in series with the IR LED gives a visual indication and should blink a couple times on each keypress Note the address of the PC port is decimal 888 LPT1 but could be 632 or 956 on some

    Original URL path: http://bowdenshobbycircuits.info/readout.htm (2016-04-26)
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  • LED Sequencers, Flashers, Clocks, Faders
    the comparator output changes at pin 7 the direction of the current changes through the capacitor which in turn causes the inverting opamp to move in the opposite direction This yields a linear ramping waveform or triangle waveform at pin 1 of the inverting opamp It is always moving slowly up or down so that the voltage on the non inverting input stays constant at 4 5 volts Adjustments to the point where the LEDs extinguish can be made by altering the resistor value at pin 3 and 6 to ground I found a 56K in place of the 47k shown worked a little better with the particular LEDs used You can experiment with this value to get the desired effect Parts List Description Mfg Part Allied Part Quantity Cost Operational Amplifier LM1458 288 1090 1 48 47K Resistor 296 2182 4 42 100K Resistor 296 5610 1 100 Ohm Resistor 895 0465 1 24 Transistor 2N3904 568 8253 1 1 22uF Capacitor 852 6516 1 07 Solderless Breadboard 237 0015 1 6 99 Red Light Emitting Diode LED 670 1224 2 0 50 Note The LED listed has a narrow viewing angle of 30 degrees and appears brightest when looking directly at it It s not a pure red color and a little on the orange side but should be brighter compared to other selections For a wider viewing angle at reduced intensity try part number 670 1257 which is viewable at 60 degrees and has a red diffused lens Construction details Layout of the solderless breadboard Refer to the drawing below the schematic diagram and note the solderless breadboard is arranged in rows labeled A J and columns numbered 1 to 65 Each group of 5 holes in the same column are the same connection so that holes A1 B1 C1 D1 and E1 are all connected together Likewise holes F1 G1 H1 I1 and J1 are all the same connection The outer rows along the length of the board are also connected together and are normally used for power supply connections However there is a break in the mid section of the outer rows so a short jumper wire connecting the mid section of the outer rows should be installed to connect the entire outer row together If you have a DMM use the low ohms range and probe the various holes to get familiar with the board layout Installing the components Orientate the LM1458 so the nook or punch mark on one edge is near column 30 and the opposite edge is near column 33 Install the LM1458 on the breadboard so the pins straddle the center section of the board and pin 1 of the IC is occupying hole E30 and pin 8 is in hole F30 The pins are numbered counter clockwise so pin 4 will be occupying F33 and pin 5 will be in E33 Possible connections for the LM1458 9 volt battery and a couple other parts is illustrated in the lower drawing of the solderless breadboard but it is not complete with all parts Refer to the schematic diagram and install the various other components so they connect to the appropriate pins of the LM1458 Use whatever connection holes are convenient For example the 22uF capacitor connects between pins 1 and 2 of the IC which occupy holes F30 F31 so it could be placed in the holes H30 H31 or J30 J31 or I30 I31 But not all parts will conveniently fit so you may have to use a short jumper wire 22 preferred to connect parts from one side of the chip to the other The board I assembled was connected this way LM1458 F30 to F33 and E30 to E33 22uF capacitor H30 to H31 47K resistor I30 to I35 47K resistor C27 to C31 47K resistor F25 to Positive battery row 47K resistor J25 to Negative Battery row 100K resistor B31 to B33 2N3904 Transistor G36 G37 G38 with emitter at G38 100 Ohm resistor D38 to F38 LED B43 to B44 Cathode at B44 LED I43 to I44 Cathode at I43 Jumper A30 to Positive battery row Jumper F36 to Positive battery row Jumper J33 to Negative battery row Jumper J43 to Negative battery row Jumper H25 to J32 Jumper J30 to J37 Jumper E27 to G31 Jumper D32 to G32 Jumper D33 to H35 Jumper C38 to C43 Jumper E44 to F44 9 Volt Battery Postive battery row to negative row The circuit below illustrates two pairs of LEDs that operate out of phase so as one pair slowly illuminate the other pair will fade Menu Automobile Interior Lights Fader This circuit is similar to the fading eyes circuit above and is used to slowly brighten and fade interior lights of older cars The circuit is based around the LM324 low power opamp which draws around 3mA of current so it won t bother the battery if left connected for extended periods The top two opamps pins 1 2 3 and 5 6 7 form a triangle wave oscillator running at about 700Hz while the lower opamp pins 8 9 10 produces a linear 5 second ramp that moves up or down depending on the position of the door switch The two transistors and associated resistors serve to limit the ramp voltage to slightly more and less than the upper and lower limits of the triangle waveform These two signals 700 hZ triangle wave and 5 second ramp are applied to the inputs of the 4th opamp pins 12 13 14 that serves as a voltage comparator and generates a varying duty cycle square wave that controls the IRFZ44 MOSFET and lamp brightness The 5 second fade time can be adjusted with the 75K resistor connected to the door switch A larger value will increase the time and a smaller value will speed it up When the door switch is closed car door open the voltage on pin 8 slowly rises above the negative peaks

    Original URL path: http://bowdenshobbycircuits.info/page5.htm (2016-04-26)
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  • 555 Timer Calculator
    low level near 0 at the end of the cycle Maximum current from the output at either low or high levels is approximately 200 mA Pin 4 Reset A low logic level on this pin resets the timer and returns the ouput to a low state It is normally connected to the supply line if not used Pin 5 Control This pin allows changing the triggering and threshold voltages by applying an external voltage When the timer is operating in the astable or oscillating mode this input could be used to alter or frequency modulate the output If not in use it is recommended installing a small capacitor from pin 5 to ground to avoid possible false or erratic triggering from noise effects Pin 6 Threshold Pin 6 is used to reset the latch and cause the output to go low Reset occurs when the voltage on this pin moves from a voltage below 1 3 of the supply to a voltage above 2 3 of the supply The action is level sensitive and can move slowly similar to the trigger voltage Pin 7 Discharge This pin is an open collector output which is in phase with the main output on pin 3 and has similar current sinking capability Pin 8 V This is the positive supply voltage terminal of the 555 timer IC Supply voltage operating range is 4 5 volts minimum to 16 volts maximum The pin connections for the 556 which is a dual 555 timer 2 in one package are shown in table below For example the two outputs for the two timers of the 556 are on pins 5 and 9 which correspond to the output pin 3 of the 555 555 556 timer 1 timer 2 Ground 1 7 7 Trigger 2 6 8 Output 3 5 9 Reset 4 4 10 Control 5 3 11 Threshold 6 2 12 Discharge 7 1 13 Power Vcc 8 14 14 The schematics below show the two basic circuits for the 555 timer Below is a pictorial view of the 555 timer wired as a LED flasher and powered with a 9 volt battery The LED will turn on during time T1 and off during time T2 The 555 circuit below is a flashing bicycle light powered with three C or D cells 4 5 volts The two flashlight lamps will alternately flash at a approximate 1 5 second cycle rate Using a 4 7K resistor for R1 and a 100K resistor for R2 and a 4 7uF capacitor the time intervals for the two lamps are 341 milliseconds T1 upper lamp and 326 milliseconds T2 lower lamp The lamps are driven by transistors to provide additional current beyond the 200 mA limit of the 555 timer A 2N2905 PNP and a 2N3053 NPN could be used for lamps requiring 500 mA or less For additional current a TIP29 NPN and TIP30 PNP could be used up to 1 amp A PR3 is a 4 5

    Original URL path: http://bowdenshobbycircuits.info/555.htm (2016-04-26)
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  • PIC Digital Clock Timer
    2 Check for 60 minutes goto Done Jump out if not 60 clrf MINUTES incf HOURS f call Daylight call Add Second Compensate for slow oscillator movlw d 13 xorwf HOURS 0 btfss STATUS 2 Check for 13 hours goto Noon Jump out if not 13 clrf HOURS incf HOURS f Set hours to 1 00 Noon movlw d 12 xorwf HOURS 0 btfss STATUS 2 Check for 12 hours goto Done Jump out if not 12 incf AMPM f bcf AMPM 1 Clear Bit 1 to stop overflow btfsc AMPM 0 AM Bit 0 clear Goto Done incf DAYS f movfw MONTH call Table xorwf DAYS 0 Check for Days Limit btfss STATUS 2 goto WeekDay clrf DAYS incf DAYS f incf MONTH f movlw d 13 xorwf MONTH 0 btfss STATUS 2 Check for new year goto WeekDay clrf MONTH incf MONTH f incf YEAR f movlw d 5 xorwf YEAR 0 btfss STATUS 2 goto WeekDay clrf YEAR incf YEAR f WeekDay incf WEEKDAY f movlw d 8 xorwf WEEKDAY 0 btfss STATUS 2 Check for new week goto Leap clrf WEEKDAY incf WEEKDAY f Set weekday to 1 Sunday Leap movlw d 2 xorwf MONTH 0 btfss STATUS 2 goto Done movlw d 29 xorwf DAYS 0 btfss STATUS 2 goto Done movlw d 4 xorwf YEAR 0 btfsc STATUS 2 goto Done movlw d 3 movwf MONTH clrf DAYS incf DAYS f Done bcf INTCON 2 swapf STATUS SAVE 0 movwf STATUS swapf TEMPW f swapf TEMPW 0 retfie End Interrupt Procedure INIT Initialize variables bsf STATUS 5 Select memory bank 1 01 bcf STATUS 6 Select memory bank 1 01 movlw b 00000000 movwf TRISB Set port B as output movlw b 01110000 movwf TRISA Set port A as output RA4 5 6 Input bsf OPTION REG 5 Select Timer0 TOCS 1 bcf OPTION REG 3 Assign prescaler to timer0 bcf OPTION REG 0 Set prescaler to 128 bcf STATUS 5 Reset to bank 0 bcf STATUS 0 Clear carry bit bcf STATUS 2 Clear zero flag bcf STATUS 1 bsf INTCON 5 Enable timer0 interrupt bcf INTCON 2 Clear interrupt flag bsf INTCON 7 Enable global interrupt movlw 07h movwf CMCON Comparators off movlw d 2 movwf HOURS Initialize hours to 2 movlw d 56 movwf MINUTES Inititlize minutes to 56 movlw d 6 movwf HOURS A Initialize alarm hours to 6 movlw d 30 movwf MINUTES A movlw d 3 movwf MONTH Initialize Month to March 7 movlw d 7 movwf DAYS movlw d 1 movwf WEEKDAY Initialize weekday to Sunday 1 clrf SECONDS clrf AMPM Initialize AMPM to AM movlw d 45 movwf TIMER LIMIT Initialize alarm timer to 45 clrf AMPM A clrf DAYLIGHT Turn off daylight savings time movlw d 2 movwf YEAR Set year to 2 Leap year 4 movlw d 18 movwf CORRECTION Add 1 second every 18 hours clrf ALARM Turn off alarm clrf TIMER clrf LIMIT clrf AMPM LED movlw h 21 movwf FSR Address

    Original URL path: http://bowdenshobbycircuits.info/pic_ck.htm (2016-04-26)
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  • PIC Digital Clock Timer
    equ 23h WEEKDAY equ 24h OPTIONS equ 25h SECONDS equ 26h HOURS START1 equ 27h Timer 1 0000 MINUTES START1 equ 28h AMPM START1 equ 29h 0001 WEEKDAY START1 equ 2ah HOURS STOP1 equ 2bh 0010 MINUTES STOP1 equ 2ch AMPM STOP1 equ 2dh 0011 WEEKDAY STOP1 equ 2eh HOURS START2 equ 2fh Timer 2 0100 MINUTES START2 equ 30h AMPM START2 equ 31h 0101 WEEKDAY START2 equ 32h HOURS STOP2 equ 33h 0110 MINUTES STOP2 equ 34h AMPM STOP2 equ 35h 0111 WEEKDAY STOP2 equ 36h HOURS START3 equ 37h Timer 3 1000 MINUTES START3 equ 38h AMPM START3 equ 39h 1001 WEEKDAY START3 equ 3ah HOURS STOP3 equ 3bh 1010 MINUTES STOP3 equ 3ch AMPM STOP3 equ 3dh 1011 WEEKDAY STOP3 equ 3eh HOURS START4 equ 3fh Timer 4 1100 MINUTES START4 equ 40h AMPM START4 equ 41h 1101 WEEKDAY START4 equ 42h HOURS STOP4 equ 43h 1110 MINUTES STOP4 equ 44h AMPM STOP4 equ 45h 1111 WEEKDAY STOP4 equ 46h TEMP equ 47h Value passed to Digits routine TENS equ 48h Value returned from Digits routine TEMPW equ 49h Used in interrupt to save w SWITCH equ 4ah Value returned from switches STATUS SAVE equ 4bh Interrupt save status TEMP1 equ 4ch Part of delay routine ALARM equ 4dh Alarm on off bit 7 set on TEMP SAVE equ 4eh Saves a copy of TEMP TIMER equ 4fh AMPM LED equ 50h FLAG equ 51h PORTC equ 52h Current state of 74HC164 register PORTC OUT equ 53h Copy of PORTC to output COUNTER1 equ 54h TEMP2 equ 55h STEPS equ 56h Current state of the 4 LED indicators FLAG1 equ 57h Program Starts here goto INIT Interrupt routine to update time org 0x04 movwf TEMPW Save w swapf STATUS 0 Get status register into w movwf STATUS SAVE Save status register bcf STATUS 5 Go to bank 0 00 incf SECONDS f Advance seconds movlw d 60 xorwf SECONDS 0 btfss STATUS 2 Check for 60 seconds goto Done Jump out if not 60 clrf SECONDS incf MINUTES f call Check events Check events where minutes are not 0 call Snooze Timer movlw d 60 xorwf MINUTES 0 btfss STATUS 2 Check for 60 minutes goto Done Jump out if not 60 clrf MINUTES incf HOURS f call Check events Check events where minutes 0 movlw d 13 xorwf HOURS 0 btfss STATUS 2 Check for 13 hours goto Noon Jump out if not 13 clrf HOURS incf HOURS f Set hours to 1 00 Noon movlw d 12 xorwf HOURS 0 btfss STATUS 2 Check for 12 hours goto Done Jump out if not 12 incf AMPM f bcf AMPM 1 Clear Bit 1 to stop overflow btfsc AMPM 0 AM Bit 0 clear Goto Done WeekDay incf WEEKDAY f movlw d 8 xorwf WEEKDAY 0 btfss STATUS 2 Check for new week goto Done clrf WEEKDAY incf WEEKDAY f Set weekday to 1 Sunday Done bcf INTCON 2 swapf STATUS SAVE 0 movwf STATUS swapf TEMPW f swapf TEMPW 0 retfie End Interrupt Procedure INIT Initialize variables bsf STATUS 5 Select memory bank 1 01 bcf STATUS 6 Select memory bank 1 01 movlw b 00000000 movwf TRISB Set port B as output movlw b 01110000 movwf TRISA Set port A as output RA4 5 6 Input bsf OPTION REG 5 Select Timer0 TOCS 1 bcf OPTION REG 3 Assign prescaler to timer0 bcf OPTION REG 0 Set prescaler to 128 bcf STATUS 5 Reset to bank 0 bcf STATUS 0 Clear carry bit bcf STATUS 2 Clear zero flag bcf STATUS 1 bsf INTCON 5 Enable timer0 interrupt bcf INTCON 2 Clear interrupt flag bsf INTCON 7 Enable global interrupt movlw 07h movwf CMCON Comparators off movlw h 22 movwf FSR Load Defaults Set all values to 0 movlw d 0 incf FSR f Increment Pointer movwf INDF movlw h 5a xorwf FSR 0 btfss STATUS 2 goto Load Defaults movlw h 21 movwf FSR Set Pointer to Time display movlw d 2 movwf HOURS movlw d 57 movwf MINUTES call Write PortC Clear shift register goto Main Timer Table Set or Reset 1 bit of portC call Parallel bsf FLAG 1 Write port C if flag set movfw COUNTER1 addwf PC 1 bsf PORTC 4 return bcf PORTC 4 return bsf PORTC 5 return bcf PORTC 5 return bsf PORTC 6 return bcf PORTC 6 return bsf PORTC 7 return bcf PORTC 7 return Parallel Set or reset bit 4 of portC if parallel option selected movlw d 0 xorwf OPTIONS 0 btfsc STATUS 2 return movfw COUNTER1 addwf PC 1 bsf PORTC 4 return bcf PORTC 4 return bsf PORTC 4 return bcf PORTC 4 return bsf PORTC 4 return bcf PORTC 4 return bsf PORTC 4 return bcf PORTC 4 return Array Data for 7 segment digits addwf PC 1 retlw b 01000000 0 retlw b 01111001 1 retlw b 00100100 2 retlw b 00110000 3 retlw b 00011001 4 retlw b 00010010 5 retlw b 00000010 6 retlw b 01111000 7 retlw b 00000000 8 retlw b 00010000 9 Main Main Loop call Display Display data call Read Port Check for switch closed movlw d 14 Check for time switch closed xorwf SWITCH 0 btfss STATUS 2 goto Set Time movlw h 21 movwf FSR clrf STEPS clrf FLAG1 call Update PortC call Wait Set Time movlw d 46 Check for time switch and RA5 closed xorwf SWITCH 0 btfss STATUS 2 goto Increment Display movlw h 21 movwf FSR clrf STEPS clrf FLAG1 call Update PortC call Wait Increment Display movlw d 13 Check for advance key pressed in run mode xorwf SWITCH 0 btfss STATUS 2 goto Function Function key not hit 13 call Wait Wait for switch to open call Increment Pointer Function movlw d 45 Ckeck for advance key pressed in setup mode xorwf SWITCH 0 btfss STATUS 2 goto Increment 100s Function key not hit 13 call Wait Wait for switch to open call Increment

    Original URL path: http://bowdenshobbycircuits.info/timer.htm (2016-04-26)
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  • Binary Clock
    connected with the secondary center tap at ground which produces about 8 volts DC across the 3300uF filter capacitor DC power for the circuit is regulated at about 5 5 using a NPN transistor 2N3053 and 6 2 volt zener diode The 2N3053 gets a little warm when several LEDs are on and may require a little top hat type heat sink A one second clock pulse is obtained by counting 60 cycles of the AC line signal This is accomplished using a CMOS CD4040 12 stage binary counter shown in light blue The 60th count is detected by the two NAND gates connected to pins 2 3 5 and 6 of the counter When all four of these lines are high the count will be 60 resulting in a high level at pin 4 of the 74HC14 which resets the counter to zero and advances the seconds counter 74HC390 shown in purple when pin 4 returns to a low state The same process is used to detect 60 seconds and 60 minutes to reset the counters and advance the minutes and hours counters respectively In both of these cases the 2 and 4 bit lines of the tens counter section will be high 20 40 60 In all three cases seconds minutes and hours a combination 10K resistor and 0 1uF capacitor is used at the input to the 74HC14 inverter to extend the pulse width to about 300uS so the counters will reliably reset Without the RC parts the reset pulse may not be long enough to reset all stages of the counter since as soon as the first bit resets the inputs to the NAND gate will no longer all be high and the reset pulse will end Adding the RC parts eliminates that possibility The reset process for the hours is a little different since for a 12 hour clock we need to reset the hours counter on the 13th count and then advance the counter one count so the display will indicate one 1 The 74HC00 quad NAND gate only has 4 sections with two inputs each so I used 3 diodes to detect the 13th hour 10 1 2 13 which drives an inverter and also a transistor inverter 2N3904 or similar The last 74HC14 inverter stage pin 12 and 13 supplies a falling edge to the hours counter which advances the hours to 1 a short time after the reset pulse from the transistor inverter ends The pulse width from pin 12 of the inverter is a little shorter than from pin 10 which ensures that the hours clock line pin 1 of yellow box will move high before the end of the reset pulse form pin 10 If it were the other way around the reset pulse may end before pin 12 of the inverter had a chance to reach a high level which would prevent the counter from advancing to 1 So it is important to use a shorter RC time

    Original URL path: http://bowdenshobbycircuits.info/clock.htm (2016-04-26)
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  • Digital Clock With Timer And Solar Panel Regulator
    a one second pulse that drives the seconds counter 74HC390 colored purple The minutes are advanced by decoding 60 seconds 40 20 and then resetting the seconds counter to 0 and at the same time advancing the minutes counter The same procedure is used to advance the hours The second half of the 4013 latch is used to indicate AM or PM and is toggled by decoding 13 hours and resetting the hours to 0 and then advancing the hours to one The clock display circuit is shown in the second drawing below and uses 6 more ICs to decode the binary data and drive four seven segment LED displays The 10s of hours digit is driven with a single 3904 transistor Two multiplexer circuits 4053 are used to manually select either minutes or seconds for the right two display digits The two switches shown between the 4053s and below the left 4053 are both part of one DPDT switch which selects either seconds or minutes for the 1X and 10X digits This switch is shown in the seconds position and the hours digits are blanked with a low signal on pin 4 of the 4511 The display can also be toggled on and off totally blank using a set reset latch made from a couple 74HC00 NAND gates A momentary DPDT switch is used to control the latch and toggle the display on or off The second pole of this switch is used on the upper drawing connected to the run stop switch to set the hours and minutes Thus this same switch performs both functions of blanking the display and setting the time The run stop switch is shown in the normal running mode and supplies a low signal to a NAND gate which prevents accidental setting the

    Original URL path: http://bowdenshobbycircuits.info/dclock.htm (2016-04-26)
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  • relay coil will be two diode drops less than the supply voltage or about 11 volts for a 12 5 volt input The common emitter configuration on the right offers the advantage of the full supply voltage across the load for most of the delay time which makes the relay pull in and drop out voltages less of a concern but requires an extra resistor in series with transistor base The common emitter circuit on the right is the better circuit since the series base resistor can be selected to obtain the desired delay time whereas the capacitor must be selected for the common collector or an additional resistor used in parallel with the capacitor The time delay for the common emitter will be approximately 3 time constants or 3 R C The capacitor resistor values can be worked out from the relay coil current and transistor gain For example a 120 ohm relay coil will draw 100 mA at 12 volts and assumming a transistor gain of 30 the base current will be 100 30 3 mA The voltage across the resistor will be the supply voltage minus two diode drops or 12 1 4 10 6 The resistor value will be the voltage current 10 6 0 003 3533 or about 3 6K The capacitor value for a 15 second delay will be 15 3R 1327 uF We can use a standard 1000 uF capacitor and increase the resistor proportionally to get 15 seconds Menu 9 Second LED Timer and Relay Circuit This circuit provides a visual 9 second delay using 10 LEDs before closing a 12 volt relay When the reset switch is closed the 4017 decade counter will be reset to the 0 count which illuminates the LED driven from pin 3 The 555 timer output at pin 3 will be high and the voltage at pins 6 and 2 of the timer will be a little less than the lower trigger point or about 3 volts When the switch is opened the transistor in parallel with the timing capacitor 22uF is shut off allowing the capacitor to begin charging and the 555 timer circuit to produce an approximate 1 second clock signal to the decade counter The counter advances on each positive going change at pin 14 and is enabled with pin 13 terminated low When the 9th count is reached pin 11 and 13 will be high stopping the counter and energizing the relay Longer delay times can be obtained with a larger capacitor or larger resistor at pins 2 and 6 of the 555 timer Menu 9 Second Digital Readout Countdown Timer This circuit provides a visual 9 second delay using a 7 segment digital readout LED When the switch is closed the CD4010 up down counter is preset to 9 and the 555 timer is disabled with the output held high When the switch is opened the timer produces an approximate 1 second clock signal decrementing the counter until the 0 count

    Original URL path: http://bowdenshobbycircuits.info/page2.htm (2016-04-26)
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